Benchmark: null vs. typeof vs. in vs. hasOwnProperty

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };

Tests:

undefined
null != obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
!! obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.99 Safari/537.36

Browser/OS: Chrome 93 on Windows 7

View result in a separate tab

Test name	Executions per second
undefined	7619748.0 Ops/sec
typeof	7518953.5 Ops/sec
in	7641676.0 Ops/sec
hasOwnProperty	6963555.0 Ops/sec
bool	7628091.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the benchmark.

**Benchmark Definition**

The benchmark measures object lookup performance using different methods: `null`, `typeof`, `in`, and `hasOwnProperty`. The script preparation code creates an object with properties `a`, `b`, `c`, `d`, and `e`.

**Options Compared**

Here are the options being compared:

1. **`null`**: Using the literal null value to check for property existence.
2. **`typeof obj.d`**: Checking if the type of `obj.d` is not "undefined".
3. **`'d' in obj`**: Using the `in` operator to check if `d` is a property of the object.
4. **`obj.hasOwnProperty('d')`**: Using the `hasOwnProperty` method to check if `d` is an own property of the object (i.e., not inherited from its prototype chain).
5. **`!! obj.d`**: Converting the boolean value of `obj.d` to a boolean using the double-boolean casting operator.

**Pros and Cons**

Here's a brief summary of each approach:

1. **`null`**: Simple and straightforward, but may incur additional overhead due to type checking.
2. **`typeof obj.d`**: Works well for primitive values, but may return "undefined" for non-existent properties, which can lead to unexpected behavior in some cases.
3. **`'d' in obj`**: Fast and efficient, as it directly checks if `d` is a property of the object. However, it's sensitive to the object's prototype chain.
4. **`obj.hasOwnProperty('d')`**: Provides more control over which properties are checked, as it only considers own properties (not inherited ones). However, it may be slower due to method call overhead.
5. **`!! obj.d`**: A concise way to convert a boolean value to a boolean, but may lead to unexpected behavior if `obj.d` is not explicitly defined.

**Library**

None of these options rely on external libraries or frameworks.

**Special JS Features**

The benchmark uses the following special JavaScript features:

1. **Double-boolean casting operator (`!!`)**: A shorthand way to convert a value to a boolean.
2. **Type checking for `null` and undefined values**: JavaScript's type checking mechanism allows us to check if a variable is null or undefined, which is useful in this benchmark.

**Other Considerations**

When choosing an object lookup method, consider the following factors:

1. **Performance**: If speed is critical, using `in` or `hasOwnProperty` might be a good choice.
2. **Accuracy**: If you need to ensure that only own properties are checked, use `hasOwnProperty`.
3. **Conciseness**: Using `!! obj.d` can make your code more concise, but may lead to unexpected behavior if not used carefully.

**Alternatives**

If you're looking for alternatives to these object lookup methods, consider:

1. **Using the `in` operator with a check for existence**: Instead of using `hasOwnProperty`, you can use the `in` operator in combination with a check for existence.
2. **Using the `Object.prototype.hasOwnProperty.call()` method**: This method provides a more explicit way to check if a property is an own property of an object.

I hope this explanation helps!

Related benchmarks:

null vs. typeof vs. in vs. hasOwnProperty (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool

Created: 2 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):